*,
*:before,
*:after {
  box-sizing: border-box;
  margin    : 0;
  padding   : 0;
}

.container {
  display    : flex;
  flex-flow  : row nowrap;
  height     : 100vh;
  align-items: stretch;
}

.container .ctrl {
  flex            : 400px 0 0;
  padding         : 1em;
  background-color: #3b4393;
  color           : #fff;
}

.container .ctrl h1 {
  text-align: center;
}
.container .ctrl .row {
  text-align: center;
}

.container .prev {
  flex   : 600px 3 1;
  padding: 1em;
}